Error of type E_ERROR in PHP 8.0+

[michaelbeil]

Describe the bug
A customer ran into an error on PHP 8.0+.

To Reproduce
Steps to reproduce the behavior on customer site:

1. Set PHP version to PHP 8.0+
2. Activate Paid Memberships Pro, and Multiple Memberships per User Add On. See this error in an email:

Expected behavior
There should not be an error.

Isolating the problem:

• Deactivated other plugins and confirmed this bug occurs when only Paid Memberships Pro 2.9.7, Multiple Memberships per User 0.8.2 is active.
• This bug happens with a default WordPress theme active, or Memberlite.

This came up in ticket 465372 on PHP 8.0.26, and this error didn't happen in my test with PHP 8.0.22.

WordPress Environment

Paid Memberships Pro 2.9.7, Multiple Memberships per User 0.8.2, WordPress 6.1.1, PHP 8.0.26

[michaelbeil]

Reopening because this happened with MMPU on a customer site.

[michaelbeil]

Another customer (ticket ID 480073) is seeing the error on PHP 8.1.

[ipokkel]

Another customer reported this error on PHP 8.2.9 (ticket ID 520486)